There is an increasing need for norms to be embedded in technology as the widespread deployment of applications such as autonomous driving and warfare becomes ever closer. Current approaches to norms in multi-agent systems tend either to simply make prohibited actions unavailable, or to provide a set of rules (principles) which the agent is obliged to follow. We argue that both these approaches are inadequate: in order to meet unexpected situations agents must be capable of violating norms, when it is appropriate to do so. This in turn requires that agents be able to reason about what they should do without reference to the norms. One way to achieve this is to conduct value based reasoning using an argumentation scheme designed for practical reasoning. Such reasoning requires that agents have an acceptable set of values and an acceptable ordering on them. We discuss what might count as an acceptable ordering on values, and how such an ordering might be determined. Law breaking is illustrated through a simple road traffic example.